1. Field of the Invention
This invention relates in general to strut framing systems and more particularly to a non-metallic, corrosion resistant framing and mechanical support system for the processes of the corrosive industries.
2. Discussion of the Prior Art
Strut framing systems have been widely used in the U.S.A. as well as internationally for nearly fifty years. However, the advent of high technology manufacturing processes during the last decade has resulted in numerous requirements for more state-of-the-art mechanical support systems. Many attempts have been made by the historical suppliers of strut systems to meet the demands of new industries, but most attempts were based on the basic industry out of which the strut systems have developed. Various grades of stainless steel strut and fasteners have been developed and are available at extremely high costs. Plated and coated steel systems have been developed from galvanizing epoxy to PVC coatings. More recently, several fiberglass strut channels have been introduced, however, their struts are designed for metallic or metallic coated fastener systems.
The strut systems of the present invention are all non-metallic, corrosion resistant framing and mechanical supports for the processes of the corrosive industries. The present invention combines two plastics design and manufacturing methods to produce a mechanical support and attachment system using all non-metallic components.
The structural strut is a specially designed fiberglass pultruded shape incorporating the use of composite structure design with a highly efficient mechanical shape to produce the strongest and stiffest support for the fastener system. The fasteners are designed of high strength composite thermoplastics and are injection molded in two halves. Their shape allows attachment to the strut support without tools, and the position locking connection provides a permanent but adjustable locking support of the process piping or ducting.
Prior to the filing of the present invention, a preliminary patent search of the prior art was performed. The following patents were found and are listed below:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 3,088,702 Orenick, et al 5/7/63 3,527,432 Lytle 9/8/70 3,721,750 Countryman 3/20/73 3,913,187 Okuda 10/21/74 4,061,299 Kurosaki 12/6/77 4,371,137 Anscher 2/1/83 ______________________________________
Perhaps the patent of most interest from this group is U.S. Pat. No. 3,527,432 issued to Lytle. Lytle shows a longitudinal channel with retaining flange for holding clamping plates which are curved to accommodate pipe or tubing. The plates are hooked to the flanges in the channel. The ends adjacent to the curved portions of the clamping plates are formed into parallel flanges with registering holes to accommodate a threaded fastener so that the clamping plates can be tightened onto the pipe. To facilitate insertion of the plates over the pipe and into the channel, one of the clamping plates is provided with two opposite hanging hooks on opposite edges, and the other plate is provided with one hanging hook. The present invention differs in many respects from Lytle. The means of holding the bands of the present invention in the flanges of the channel is different; the means of fastening and holding the pipe or duct is different; also, the bands used in the present invention are much different than Lytle's plates both in structure and result. Further, Lytle does not contemplate use of his support system in a corrosive application.
U.S. Pat. No. 3,721,750 issued to Countryman shows a plastic strapping fastener. It is much different than the present invention in structure and function. The other patents found in the search relate to the general area of fastening systems, but in applicant's opinion, either alone or in combination, do not disclose the key elements of applicant's invention as disclosed herein.
A patent that became a key reference to the parent of this application was by Clark (U.S. Pat. No. 3,226,069 issued 12/28/65). Applicant would like to point out a key and critical distinction between Clarke and their invention. It lies in the top portion of the support bands and more specifically in the contact between the flanges on the hanger and the flanges on the support element. Applicant is aware that merely changing Clark's hangers and support element to thermoplastic and/or fiberglass would not result in patentability. If this were done, Clarke's invention duplicated in plastic and/or fiberglass would fail due to tensile load concentrations at points in his anchors 26 and flanges 22. Clarke's system relies on point and line contact of the anchors 26 and flanges 22, and suggests the use of ear 26b if flanges 24 are rounded, and ear 26a if flanges 24 are straight. (See Clarke, col 3, lines 9-18). In metal, this point and line contact would be acceptable and support the required weight, since metal has sufficient tensile strength to resist the tendency to bend the anchors 26 whether they are shaped as in 26a or 26b, and whether flanges 22 are rounded or straight. Stress concentration would occur in ear shape 26a at the point which the ear 26a meets the medial portion 26c, and in ear shape 26b similarly at the points where the ear 26b changes direction, and at its tip. In either case, flange 24 whether rounded or straight would experience tensile stress due to bending where the flange 24 meets the sides of support 10. Clarke's anchors 26 and flanges 24 are typical of what is conventionally available in the metal hanger art. This system if duplicated in plastic and/or fiberglass would fail when the conventionally required loads were placed upon it. A more comprehensive interface between the support element and hanger is needed, which is supplied by applicants' invention.